Heat insulating liners for a wide variety of chambers and operating environments present serious problems owing to the high operating temperatures and hostile conditions commonly encountered in such chambers. Traditionally and historically chambers of this type have been lined with various types of bricks, castables or other dense refractories compounded in efforts to withstand high operating temperatures. These linings have many shortcomings and disadvantages well known to those skilled in this art including objectionably high weight, the need for high strength supporting structure, spalling, cracking and shattering, poor thermal properties, high initial assembly, maintenance and replacement costs, high heat storage capacity, poor insulating ability, and others. In recent years lightweight non-rigid linings in a variety of types and construction have come into general use. Certain of these linings are made of ceramic fiber material deposited on a moving conveyor as in the manner disclosed in the U.S. patent to Malone U.S. Pat. No. 3,615,964. Such a blanket has a thickness of a fraction of an inch up to two inches, a density of three to eight pounds per cubic foot and is readily flexed and coiled until ready for use. Another technique involves vacuum forming mats of refractory fibers into convenient size by vacuum deposition from an aqueous slurry. Denser and more compact mats can be made in this manner up to a maximum thickness of two to two and one half inches. Efforts to make thicker mats have not been successful prior to the teachings disclosed in the co-pending U.S. application Ser. No. 919,230, now U.S. Pat. No. 4,202,148, filed June 26, 1978 by Carl E. Frahme and Gary E. Wygant. Heat insulating mats made by either of the aforementioned techniques provide inadequate insulation for many uses unless applied over an existing lining or unless other techniques are resorted to to increase the thickness.
Designers familiar with the aforementioned problems have made a variety of proposals for improved modes of utilizing refractory fiber mats and blanket material. Typical of these are the disclosures in such patents as Sauder U.S. Pat. No. 3,706,870; Sauder U.S. Pat. No. 3,819,468; Balaz U.S. Pat. No. 3,832,815; Brady U.S. Pat. No. 3,854,262; Monaghan U.S. Pat. No. 3,892,396; Shelley U.S. Pat. No. 3,930,916; Sauder U.S. Pat. No. 3,940,244; Byrd U.S. Pat. No. 3,952,470; Greaves U.S. Pat. No. 3,990,203; Sauder U.S. Pat. No. 3,993,237; Byrd U.S. Pat. No. 4,001,996; Woodruff U.S. Pat. No. 4,122,644; Werych U.S. Pat. No. 4,246,852; Werych U.S. Pat. No. 4,249,888 and Dunlap U.S. Pat. No. 4,248,023. For the most part these proposals concern different modes for holding strips of the aforementioned refractory fiber blanket material assembled in strips in side-by-side relation to some type of supporting frame or backing in an assembly operation carried out after forming the mat. In the usual case the mounting is designed to compress the fiber strips transversely of their thickness in order to increase the density and to compensate for shrinkage at higher temperatures. All of these techniques involve objectionably high labor, assembly and material costs and provide a lining product having inferior performance and heat insulating characteristics. Two of the above mentioned patents propose vacuum forming insulating fibers around an anchorage having provision for attaching the resulting module to a furnace wall but each is subject to shortcomings and disadvantages avoided by this invention. The most recent one of the above mentioned prior patents proposes a module the main body of which comprises a stack of individual layers hand assembled and secured together by adhesive or by a metal fastener piercing some or all layers. The metal fastener must be installed subsequent to the assembly of the core layers and the embracing shell further adding to the cost of manufacture.